Bailibo Testing - Analysis of High Temperature Conductivity Testing Technology for Graphite Materials

Graphite materials are widely used in aerospace, energy, electronic devices and other fields due to their unique physical and chemical properties. Electrical conductivity is one of the key performance indicators of graphite materials, and its testing methods and technical requirements directly affect the application effect of the material.

1. Basic characteristics of electrical conductivity of graphite materials

The electrical conductivity of graphite is a hundred times higher than that of ordinary non-metallic minerals, and its thermal conductivity exceeds that of steel, iron, lead and other metal materials. The melting point of graphite is 3850±50℃ and the boiling point is 4250℃. Even after ultra-high temperature arc burning, the weight loss is very small and the thermal expansion coefficient is also very small. The thermal conductivity decreases as the temperature increases, and even at extremely high temperatures, graphite becomes a thermal insulator.

2. Main methods of conductivity testing

Currently, the commonly used methods for testing conductivity of graphite materials include the four-probe method and the DC method. The two-probe method is easily affected by contact resistance, while the four-probe method reduces contact resistance interference by separating the current and voltage loops and makes the measurement more accurate. The four-probe method is the most commonly used high-precision measurement method in laboratories. Four probes press current on the sample, and its resistivity is calculated by measuring the voltage between the probes at both ends and the current between the probes on both sides.

3. Testing technology in high-temperature environment

The four-probe method high-temperature resistivity testing system is equipped with thermocouple temperature detection and can measure material resistivity up to 1700°C. The system includes high-temperature 4-probe fixtures, vacuum atmosphere 4-probe fixtures and other components, and is suitable for electrical performance testing of a variety of materials. Some studies have shown the curve of the conductivity of a graphite composite system changing with time under different temperature conditions. When the temperature increases, the conductivity of the system significantly increases.

4. Test application and significance

The conductivity of graphite materials in practical applications will directly affect the application effect of the materials. In high-temperature tests, changes in electrical conductivity can reflect the evolution of the material's internal conductive network during heat treatment. The test results can be used to evaluate the thermal conductivity of the material, optimize the preparation process, and provide data support for the application of the material in energy storage, photovoltaics, electronic devices and other fields.

5. Testing Precautions

During the testing process, attention should be paid to the impact of sample preparation, instrument and equipment calibration, temperature control and other factors on the test results. The four-probe method may not fully reflect the pole piece resistance when the coating is thick, and there is a certain error, but it is still a commonly used testing method. During high-temperature testing, factors such as thermal expansion and chemical reactions of materials will also affect the accuracy of the test results. Appropriate test conditions need to be selected based on specific application scenarios.